Sometimes the term also includes the inhabitants of Tenochtitlan's two principal allied city-states, the Acolhuas of Texcoco and the Tepanecs of Tlacopan, who together with the Mexica formed the Aztec Triple Alliance which controlled what is often known as the "Aztec Empire". In this meaning it is possible to talk about an Aztec civilization including all the particular cultural patterns common for most of the peoples inhabiting Central Mexico in the late postclassic period. The Triple Alliance formed a tributary empire expanding its political hegemony far beyond the Valley of Mexico, conquering other city states throughout Mesoamerica.